Air flow measuring device

ABSTRACT

An air flow measuring device includes a housing, a sensing part, a temperature sensor, a supporting member, and a protective projection. The housing defines a bypass flow passage which guides a part of air flowing in a duct. The sensing part is disposed in the bypass flow passage to measure a flow rate of air in the bypass flow passage. The sensor detects temperature of air flowing in the duct outside the housing. The supporting member supports the sensor at a predetermined measurement position. The protective projection is a projection, which projects outward from a side surface of the housing and is formed by mold removal in one direction. An end of the protective projection is located outward of the sensor. The protective projection makes contact with an object approaching the sensor from outside the housing to limit contact of the object with the sensor.

CROSS REFERENCE TO RELATED APPLICATION

This application is based on Japanese Patent Application No. 2014-92307filed on Apr. 28, 2014, the disclosure of which is incorporated hereinby reference.

TECHNICAL FIELD

The present disclosure relates to an air flow measuring device includinga temperature sensor that measures temperature of air in a duct.

BACKGROUND

Conventionally, as a flow measuring device, there is a device includinga housing having a bypass flow passage that guides a part of air(mainstream) flowing in a duct, a temperature sensor for measuringtemperature of the air flowing in the duct outside the housing, and aprotection cover that is provided integrally with the housing to protectthe temperature sensor (see, e.g., JP2010-185793A).

The air flow measuring device is inserted into the duct through anattachment hole formed at the duct so as to be disposed in the duct.When a side facing an opening edge of the attachment hole at the time ofthe insertion of the device is referred to as a front side of thetemperature sensor, and an insertion direction side is referred to as alower side of the temperature sensor, a protection member has an L-shapein section surrounding the front side and the lower side of thetemperature sensor. The protection cover having such a shape preventscontact of the temperature sensor with the duct at the time of theinsertion of the device into the attachment hole, and also serves as aprotection member that protects the temperature sensor from objectsapproaching the temperature sensor such as fingers and other members.

However, the protection cover in an L-shape in section has a complicatedmold structure at the time of resin-molding. In Japanese Patent No.3242286, there is described an art whereby a protection wall projectingfrom a side surface of the housing is provided on a lower side of thetemperature sensor to prevent the contact of the temperature sensor withthe duct at the time of the insertion into the attachment hole.Nevertheless, this protection wall has an insufficient protectivefunction because its end is located inward of the temperature sensor.

SUMMARY

The present disclosure addresses at least one of the above issues. Thus,it is an objective of the present disclosure to configure a protectionmember for a temperature sensor such that resin-molding by a simple moldstructure can be performed in a flow measuring device including thetemperature sensor.

To achieve the objective of the present disclosure, there is provided anair flow measuring device adapted to be attached to a duct. The air flowmeasuring device includes a housing, a sensing part, a temperaturesensor, a supporting member, and a protective projection. The housingdefines a bypass flow passage which takes in a part of air flowing inthe duct. The sensing part is disposed in the bypass flow passage tomeasure a flow rate of air in the bypass flow passage. The temperaturesensor detects temperature of air flowing in the duct outside thehousing. The supporting member supports the temperature sensor at apredetermined measurement position. The protective projection is aprojection, which projects outward from a side surface of the housingand is formed by mold removal in one direction. An end of the protectiveprojection is located outward of the temperature sensor. The protectiveprojection makes contact with an object approaching the temperaturesensor from outside the housing to limit contact of the object with thetemperature sensor.

Accordingly, the temperature sensor can be protected by a structure thatenables resin-molding in a simple mold structure of the “projection thatis formed by mold removal in one direction”.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a schematic sectional view illustrating an air flow measuringdevice in accordance with an embodiment;

FIG. 2 is a side view illustrating the air flow measuring device of theembodiment;

FIG. 3 is a plan view illustrating the air flow measuring device viewedfrom an upstream side in a mainstream direction according to theembodiment;

FIG. 4A is a diagram illustrating operation of the air flow measuringdevice of the embodiment;

FIG. 4B is a diagram illustrating FIG. 4A viewed from the upstream sidein the mainstream direction according to the embodiment; and

FIG. 5 is a partially enlarged view illustrating a side view of an airflow measuring device in accordance with a modification.

DETAILED DESCRIPTION

An embodiment will be explained in detail in the following description.

A configuration of an air flow measuring device 1 of the embodiment willbe described with reference to FIGS. 1 to 4B. The air flow measuringdevice 1 is, for example, an air flow meter that measures an amount ofintake air to an engine for an automobile, and is used by attachment toa duct D defining an intake passage to the engine for the automobile. Anattachment hole Da having a round shape opens on a pipe wall of the ductD, and the air flow measuring device 1 is inserted and thereby disposedin the duct D through the attachment hole Da.

The air flow measuring device 1 is configured integrally by, forexample, a base portion 2, a housing 3, a flow sensor (sensing part) 4,a temperature sensor 5, a supporting member 6, a protective projection7, which will be explained in the following description.

The base portion 2 is fitted in the attachment hole Da, and includes anouter peripheral surface opposed to an inner peripheral surface of theattachment hole Da. A circumferential groove is formed on this outerperipheral surface, and a clearance between the inner peripheral surfaceof the attachment hole Da and the outer peripheral surface of the baseportion 2 is sealed with an O-ring 2 a disposed in the circumferentialgroove (see FIG. 1).

The housing 3 extends from the base portion 2 into the duct D to bedisposed in the duct D, and defines a bypass flow passage 11 that guidesa part (measurement air) of intake air flowing in the duct D. In thefollowing description, a direction of a flow (mainstream) of air flowingin the duct D is referred to as a mainstream direction. Furthermore, adirection in which the housing 3 extends from the base portion 2 isreferred to as a lower side in a height direction, and an opposite sideof this is referred to as an upper side in the height direction. Inaddition, a wall surface of the housing 3 that is along the mainstreamdirection and extends in the height direction is referred to as ahousing side surface 3 a. In the present embodiment, the heightdirection and the mainstream direction are perpendicular to each other.The housing 3 is formed by injection-molding.

The bypass flow passage 11 will be described below. The bypass flowpassage 11 includes an inlet port 12 that opens toward an upstream sidein the flow (mainstream) of air flowing in the duct D, and a dischargeport 13 for intake air that opens toward a downstream side in themainstream. For example, the bypass flow passage 11 guides the intakeair around from the inlet port 12 toward the discharge port 13 (see FIG.1). The bypass flow passage 11 includes a region 14 where the fluidflows reversely to a forward direction in the mainstream direction, andthe flow sensor 4 is disposed in this region 14.

A dust discharge passage 15 for discharging dust is connected to thebypass flow passage 11 on an upstream side of the flow sensor 4. Thedust which has entered into the bypass flow passage 11 returns into theduct D through a dust discharge port 16 via the dust discharge passage15 without flowing toward the flow sensor 4.

The discharge port 13 is formed to open on a housing side surface on adownstream side in the mainstream. The fluid released from the dischargeport 13 flows along the housing side surface 3 a (see FIG. 2). Thebypass flow passage 11 branches into two passages on a downstream sideof the flow sensor 4, and the discharge ports 13 are providedrespectively on both side surfaces of the housing 3.

On the housing side surface 3 a, there is provided a flow straighteningplate 17 for straightening the fluid discharged from the discharge port13 and the fluid flowing around the discharge port 13.

The flow sensor 4 outputs an electrical signal (e.g., voltage signal)according to a flow rate of air flowing through the bypass flow passage11. Specifically, the flow sensor 4 includes a heater element and athermosensitive element formed by a thin film resistor on a membraneprovided for a semiconductor substrate, and these elements are connectedto a circuit board (not shown) accommodated in the base portion 2.

The temperature sensor 5 is a temperature detecting element (bobbin typeresistor) that detects the temperature of air flowing in the duct D. Alead wire 20 extends from both ends of the temperature sensor 5, and thelead wire 20 is connected to the circuit board (not shown) accommodatedin the base portion 2. The temperature sensor 5 is supported by thesupporting member 6 at a predetermined measurement position that isspaced away in a direction perpendicular to the housing side surface 3 aoutside the housing side surface 3 a.

The supporting member 6 is electrically connected to the circuit boardof the base portion 2. The supporting member 6 extends from the baseportion 2 in a direction (lower side) in which the housing 3 extends,and holds the temperature sensor 5 at its end portions. In the presentembodiment, the lead wire 20 serves as the supporting member 6, andsupports the temperature sensor 5 at the predetermined measurementposition. Specifically, the lead wire 20 projects from both the ends ofthe temperature sensor 5 to be bent toward the upper side along the way,and its end portions are connected to the circuit board. As a result,the lead wire 20 extends toward the lower side from the base portion 2to serve as the supporting member 6 that holds the temperature sensor 5at its end portions (lower end portions). In addition, the supportingmember 6 may include a terminal extending from the base portion 2 towardthe lower side, and the lead wire 20 connected to the terminal (seeJP2010-185793A).

A fixing part 20 a that is crimped and fixed to a supporting projection22 projecting from the housing side surface 3 a is provided for the partof the lead wire 20 that extends from the base portion 2 toward thelower side. Characteristics of the embodiment will be described below.The air flow measuring device 1 includes the protective projection 7which will be explained in the following description. The protectiveprojection 7 is a projection that projects outward from the housing sidesurface 3 a, and is formed by injection-molding at the time of formingof the housing 3. The protective projection 7 has a shape that can beformed by mold removal in one direction. Therefore, the projection 7 isformed in a shape without having a flange, hook shape or the like. Theleading end of the protective projection 7 is located outward of thetemperature sensor 5. The protective projection 7 makes contact with anobject approaching the temperature sensor 5 from the outside of thehousing 3 to prevent the object from coming into contact with thetemperature sensor 5.

In the present embodiment, the protective projection 7 is a projectionprojecting in a direction perpendicular to the housing side surface 3 a,and its end position is located outward of the temperature sensor 5 (ona side away from the housing side surface 3 a) (see FIG. 3).

There are provided more than one protective projection 7, and theprotective projections 7 are arranged to surround the temperature sensor5. The protective projection 7 is disposed at a position that does notinterfere with the lead wire 20 (supporting member 6).

In the present embodiment, one rod-shaped protective projection 7 isprovided respectively on an upstream side of the temperature sensor 5 inthe mainstream direction and on a downstream side of the temperaturesensor 5 in the mainstream direction. The protective projection 7provided on an upstream side of the temperature sensor 5 in themainstream direction is referred to as an upstream-side protectiveprojection 7A. The protective projection 7 provided on a downstream sideof the temperature sensor 5 in the mainstream direction is referred toas a downstream-side protective projection 7B. The projection lengths(sizes in a direction perpendicular to the housing side surface 3 a) ofthe upstream-side protective projection 7A and the downstream-sideprotective projection 7B are the same. In addition, the flowstraightening plate 17 which is positioned closer to the temperaturesensor 5 also serves as the protective projection 7.

Accordingly, in the present embodiment, there are provided the threeprotective projections 7 of the upstream-side protective projection 7A,the downstream-side protective projection 7B, and the flow straighteningplate 17. When viewed from the direction perpendicular to the housingside surface 3 a, the temperature sensor 5 is located in a regionsurrounded with those protective projections 7 (see FIG. 2).

The upstream-side protective projection 7A and the temperature sensor 5are provided at positions that do not overlap with each other whenviewed from the mainstream direction. Specifically, the upstream-sideprotective projection 7A and the temperature sensor 5 differ in positionin the height direction. A projection area that is formed by projectingthe upstream-side protective projection 7A onto a projection planeperpendicular to the mainstream direction, and a projection area that isformed by projecting the temperature sensor 5 onto this projection planedo not overlap with each other. The upstream-side protective projection7A and the downstream-side protective projection 7B are provided at thesame positions in the height direction.

The supporting member 6 includes a bent part 6 a that is inflected tobring the temperature sensor 5 closer to the housing side surface 3 a.Specifically, a part of the supporting member 6 that projects from thebase portion 2 and leads to the bent part 6 a extends parallel to thehousing side surface 3 a. A part of the supporting member 6 that is on alower side of the bent part 6 a is inclined relative to the housing sidesurface 3 a and extends to come closer to the housing side surface 3 afurther on a lower side. The fixing part 20 a is provided on an upperside of the bent part 6 a.

Effects of the embodiment will be described below. The air flowmeasuring device 1 of the present embodiment includes the protectiveprojection 7 which is a projection that projects outward from thehousing side surface 3 a and is formed by mold removal in one direction.The end of the protective projection 7 is located outward of thetemperature sensor 5, and the protective projection 7 makes contact withan object approaching the temperature sensor 5 from the outside of thehousing 3 to prevent the object from coming into contact with thetemperature sensor 5. Accordingly, the temperature sensor 5 can beprotected by a structure that enables resin-molding in a simple moldstructure of the “projection that is formed by mold removal in onedirection”. Application is possible also to formation of the housing 3by a die slide injection molding (abbreviated as DSI) method, and acomplex mold structure does not need to be added to form the protectiveprojection 7.

The temperature sensor 5 is positioned outside the housing 3, and thusneeds to be protected from the object (e.g., fingers, duct or othermembers) approaching the temperature sensor 5 from the outside of thehousing 3. The end of this protective projection 7 is located outward ofthe temperature sensor 5. Accordingly, if, for example, a finger Fapproaches from the direction perpendicular to the housing side surface3 a, the finger F makes contact with the protective projection 7 andcannot come any closer to the housing side surface 3 a (see FIGS. 4A and4B). Thus, the protective projection 7 prevents the contact of thefinger F with the temperature sensor 5. For this reason, the finger Fcan be prevented from coming into contact with the temperature sensor 5.

Particularly, by surrounding the temperature sensor 5 by more than oneprotective projection 7 as in the embodiment, a function of protectingthe temperature sensor 5 can be improved. By making smaller a distancebetween the protective projections 7, contact of a smaller object withthe temperature sensor 5 can be prevented.

The upstream-side protective projection 7A and the temperature sensor 5are provided at positions that do not overlap with each other whenviewed from the mainstream direction. Accordingly, the mainstream flowsdirectly into the temperature sensor 5, and thus the temperature of airflowing inside the duct D can be measured with high accuracy.

The supporting member 6 includes a bent part 6 a that is inflected tobring the temperature sensor 5 closer to the side surface 3 a of thehousing 3. Accordingly, the configuration of positioning the end of theprotective projection 7 outward of the temperature sensor 5 is easilyrealized.

Modifications to the above-described embodiment will be explained below.In the embodiment, the flow straightening plate 17 serves also as theprotective projection 7. However, the flow straightening plate 17 doesnot need to serve as the protective projection 7. In the embodiment, thetwo protective projections 7 (the upstream-side protective projection7A, and the downstream-side protective projection 7B) are provided toposition the temperature sensor 5 therebetween in the mainstreamdirection. Nevertheless, the arrangement of the protective projections 7to surround the temperature sensor 5 is not limited to the aspect in theembodiment. For example, the temperature sensor 5 may be surrounded withthree or more rod-shaped protective projections 7.

A single protective projection 7 may only be provided near thetemperature sensor 5. For example, the present disclosure may include anaspect in which the single rod-shaped protective projection 7 isprovided on the housing side surface 3 a on an upper side of theposition of the temperature sensor 5 as illustrated in FIG. 5. In thiscase as well, the function of protecting the temperature sensor 5 can befulfilled. It is noted that surrounding the temperature sensor 5 by morethan one protective projection 7 as in the embodiment has a higherprotecting function.

The bypass flow passage 11 of embodiment is a flow passage that guidesthe intake air around from the inlet port 12 toward the discharge port13, and includes the region 14 where the fluid flows reversely to theforward direction in the mainstream direction. However, the aspect forthe bypass flow passage 11 is not limited to this. The presentdisclosure may include an aspect in which the bypass flow passage 11 isformed from the inlet port 12 along a forward flow in the mainstreamdirection such that the bypass flow passage 11 guides a part of themainstream and does not make the air flow around, and the intake airentering from the inlet port 12 flows along the forward flow in themainstream direction to be discharged.

While the present disclosure has been described with reference toembodiments thereof, it is to be understood that the disclosure is notlimited to the embodiments and constructions. The present disclosure isintended to cover various modification and equivalent arrangements. Inaddition, while the various combinations and configurations, othercombinations and configurations, including more, less or only a singleelement, are also within the spirit and scope of the present disclosure.

What is claimed is:
 1. An air flow measuring device adapted to beattached to a duct, the air flow measuring device comprising: a housingthat defines a bypass flow passage which guides a part of air flowing inthe duct; a sensing part that is disposed in the bypass flow passage tomeasure a flow rate of air in the bypass flow passage; a temperaturesensor that detects temperature of air flowing in the duct outside thehousing; a supporting member that supports the temperature sensor at apredetermined measurement position; and a protective projection that isa projection, which projects outward from a side surface of the housingand is formed by mold removal in one direction, wherein: an end of theprotective projection is located outward of the temperature sensor; andthe protective projection makes contact with an object approaching thetemperature sensor from outside the housing to limit contact of theobject with the temperature sensor.
 2. The air flow measuring deviceaccording to claim 1, wherein the protective projection is one of aplurality of protective projections that are arranged to surround thetemperature sensor.
 3. The air flow measuring device according to claim2, wherein: a flow direction of air flowing in the duct is a mainstreamdirection; and the plurality of protective projections are provided onan upstream side of the temperature sensor in the mainstream directionand on a downstream side of the temperature sensor in the mainstreamdirection.
 4. The air flow measuring device according to claim 1,wherein: a flow direction of air flowing in the duct is a mainstreamdirection; the protective projection which is provided on an upstreamside of the temperature sensor in the mainstream direction is anupstream-side protective projection; and the upstream-side protectiveprojection and the temperature sensor are provided at positions that donot overlap with each other when viewed from the mainstream direction.5. The air flow measuring device according to claim 1, furthercomprising a base portion that is fitted in an attachment hole whichopens on a wall surface of the duct to be attached to the duct, wherein:the housing is disposed to extend from the base portion to inside of theduct; the supporting member is a member that is disposed to extend fromthe base portion in a direction in which the housing extends, and holdsthe temperature sensor at an end portion of the supporting member; andthe supporting member includes a bent part that is inflected to bringthe temperature sensor closer to the side surface of the housing.